A common method of treating temporary or chronic pain is by application of heat to the afflicted area. Such heat treatments are used as a means of therapy for conditions which include aches, stiffness in muscles and joints, nerve pain, rheumatism and the like. These treatments include the use of whirlpools, hot towels, hydrocollators, heating pads and elastic compression bands. Many of these devices employ reusable thermal packs containing, e.g., water and microwaveable gels. In general, such devices which require the thermal source to be replenished are inconvenient to use. Further, many of these thermal units or devices do not provide long lasting heat and also do not maintain a consistent temperature over long periods of time. The skin temperature needs to be maintained from about 38.degree. C. to about 41.degree. C. but not above 45.degree. C., as tissue damage occurs above 45.degree. C., to achieve the desired therapeutic benefits.
The beneficial therapeutic effects from this administration of heat diminishes after the heat source is removed; therefore, it is desirable to provide a sustained heat source to the afflicted area for as long as possible, preferably for about eight hours. Disposable heat packs based on iron oxidation, such as those described in U.S. Pat. Nos. 4,366,804, 4,649,895, 5,046,479 and Re. 32,026, are known and can provide long-lasting heat. However, such devices have proven not totally satisfactory because many of these devices cannot maintain a consistent and controlled temperature and/or such thermal devices are bulky and have unsatisfactory physical dimensions which hinder their effectiveness. Specifically, such devices cannot be easily incorporated into wraps which can comfortably conform to various body contours and hence deliver inconsistent, inconvenient and/or uncomfortable heat application to the body.
The present inventors have found that heat cells, based on a specific iron oxidation chemistry and having specific physical dimensions and fill characteristics, provide long lasting heat generation with improved temperature control. The heat cells of the present invention contain a particulate heat generating material which substantially fills the available cell volume within the cell reducing any excess void volume thereby minimizing the ability of the particulate matter to shift within the cell. This is accomplished without the need for any differential pressure across the cell wall. These heat cells, because of their adaptable physical dimensions, can be easily incorporated into disposable body wraps and the like which adapt to a wide variety of body contours, thus providing consistent, convenient, and comfortable heat application.
It is therefore an object of the present invention to provide heat cells which provide a controlled and sustained temperature and which reach their maximum temperature quickly. It is a further object of the present invention to provide heat cells which can be easily incorporated into disposable body wraps which adapt to a wide variety of body contours providing consistent, convenient and comfortable heat application.
These objectives and additional objectives will become readily apparent from the detailed description which follows.